A chemically amplified positive resist composition is a pattern formation material in which an acid is generated in the exposed area upon irradiation of radiation, for example, a far ultraviolet ray, and solubility in a developer between the exposed area and unexposed area is differentiated by a reaction using the acid as a catalyst, whereby a pattern is formed on a substrate.
Since the composition is mainly composed of a resin having as a basic skeleton, polythydroxystyrene) that has a small absorption in a region of 248 nm, a good pattern with high sensitivity and high resolution is formed, when a KrF excimer laser is used as a light source for exposure. Thus, the composition is superior to a conventional resist composition using a naphthoquinonediazide/novolac resin.
When a light source having a shorter wavelength, e.g., an ArF excimer laser (193 nm) is used for exposure, on the other hand, since an aromatic group-containing compound essentially has a large absorption in a region of 193 nm, the above-described chemically amplified composition is still insufficient.
The use of poly(meth)acrylate as a polymer having a small absorption in a wavelength range of 193 nm is described in J. Vac. Sci. Technol., B9, 3357(1991). The polymer has, however, a problem in that resistance to dry etching ordinarily performed in a semiconductor production process is low in comparison with conventional phenolic resins having an aromatic group.
Also, a triarylsulfonium salt acid generator and a phenacylsulfonium salt acid generator are known as acid generators for chemically amplified positive resist composition. However, these acid generators are low in sensitivity, since the . triarylsulfonium salt acid generator has a large absorption at a wavelength of 193 nm and the phenacylsulfonium salt acid generator is inferior in the acid-generating property. According to the request on the miniaturization of semiconductor chips in recent years, patterns of semiconductor reach to a fine range of from 0.13 to 0.35 μm. However, conventional resist compositions have a problem in that the resolution of pattern is poor owing to factors, for example, edge roughness of line pattern. The term “line edge roughness” used herein means unevenness of edge which results from irregular fluctuation of an edge of top portion and an edge of bottom portion in the direction vertical to the line due to the characteristics of resist, when the pattern is observed from just above.
Further, other characteristics, for example, halftone exposure aptitude are not satisfied according to conventional techniques. The term “halftone exposure aptitude” used herein means that when the exposure is performed using a halftone phase sift mask, sidelobe, which is a phenomenon wherein a hole is apt to be made due to weakening of surface in the unexposed area, does not occur or hardly occur. The halftone exposure aptitude is also referred to as sidelobe resistance. Moreover, it is also desired to restrain development defect in conventional resist composition. For instance, resist compositions containing an acid-decomposable resin having an alicyclic hydrocarbon structure and a single basic compound are described, for example, in JP-A-10-111569 and JP-A-11-305444 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”). However, there is room for improvement, for example, in the edge roughness of pattern and development defect.